We and a number of other investigators in the Boston-Cambridge area are now utilizing stable isotopes (15N and 13C) as tracers in a broad series of ongoing investigations concerned with an exploraton of the effects of burn trauma on metabolism and nutrient utilization in human subjects, with particular reference to burn stress, protein-energy intakes (oral and intravenous), the alterations of the metabolic reactions to trauma brought about by aging, the metabolic alterations in sepsis, and the proportion of carbohydrate, protein, and fat most effective for nutritional support. These recent studies have expanded considerably our understanding of various aspects of the interrelationships among, and regulation of, carbohydrate (glucose), lipid, and protein metabolism. The major analytical technique used by us for determination and assay of stable isotopes has been accomplished with the aid of an isotope-ratio mass spectrometer. Further significant advances in our research, as well as those by our collaborators, can only be accomplished by application of the mass fragmentography technique (multiple ion detection (MID). In this proposal, a request is made for the purchase of an analytical gas chromatograph/mass spectrometer/data system. It is anticipated that the application of this equipment in our overall research program would generate significant advances in the understanding of human metabolism under conditions of stress and trauma.